Nitrogen-containing organosilicon materials and methods for producing them



United States Patent 3,494,951 NITROGEN-CONTAINING ORGANOSILICONMATERIALS AND METHODS FOR PRO- DUCING THEM Abe Berger, Schenectady,N.Y., assignor to General Electric Company, a corporation of New York NoDrawing. Filed Sept. 20, 1967, Ser. No. 669,298 Int. Cl. C07f 7/10 U.S.Cl. 260-4482 3 Claims ABSTRACT OF THE DISCLOSURE A method is providedfor making various nitrogen-containing organosilicon compounds, such assilylorganoisocyanates, the corresponding carbamate and isocyanurates.The method involves contacting silylorganohalide and a metal cyanate inthe presence of a suitable aprotic solvent. Nitrogen-containingorganosilicon compounds are provided having silicon and nitrogen atomsseparated by a divalent hydrocarbon radical. In instances where aurethane is desired, an appropriate aliphatic monohydric alcohol can beutilized in combination with the silylorganohalide and metal cyanate.The subject nitrogen-containing organosilicon compounds can be utilizedfor making silicon-organic copolymers and as treating agents forimparting water repellency to various substrates.

The present invention relates to various methods of making certainnitrogen-containing organosilicon materials, based on contacting a metalcyanate and a silylorganohalide at elevated temperatures. Moreparticularly, the present invention relates to certainsilylorganocarbamates and to the employment of these materials to makesilylorganoisocyanates.

Prior to the present invention, methods for making certainsilylisocyanates involved the direct reaction between a halosilane and ametal cyanate. For example, Klein Patent 2,532,559 shows the use of leadcyanate with dimethyldichlorisilane to producedimethyldiisocyanatosilane. Those skilled in the art known that suchsilylisocyanates are hydrolytically unstable because the isocyanateradical is directly attached to silicon. Speier Patent 3,170,891 shows amethod for making silylorganoisocyanates having the silicon atom and theisocyanate radical separated by a divalent hydrocarbon radical. Reactionis eifected between a silicon hydride and an olefinically unsaturatedisocyanate, such as allylisocyanate. Experience has shown that althoughthe silylorganoisocyanates made by Speiers method, having asilicon-carbon bond, instead of a silicon-nitrogen bond, have improvedhydrolytic stability, the method of Speier is undesirable for a varietyof reasons. For example, it has been found that silicon hydride additionof a silane to an olefinically unsaturated isocyanate, Where the siliconhas reactive radicals, such as alkoxy attached to silicon, often resultsin undesirable side reactions between the alkoxy radicals and isocyanateradicals. In addition, Speiers method is economically unattractivebecause of the expense of olefinically unsaturated isocyanates, such asallylisocyanate.

The present invention is based on the discovery thatsilylorganoisocyanates of the formula,

(1) (RO R' SiR"NCO can be made by effecting the pyrolysis of thecorresponding carbamate as shown by the following equation,

ll (R0)a-sR'aSiR"NHCOR formula (1) ROE where R is an alkyl radicalhaving from 1 to 8 carbon atoms, R is selected from monovalenthydrocarbon radi- 3,494,951 Patented Feb. 10, 1970 ice to a temperaturewhich is suflicient to produce a mixture consisting essentially of (A)said silylorganocarbamate, (B) said silylorganoisocyanate of Formula 1,and (C) an aliphatic monohydric alcohol, (2) continuously distillingsaid mixture of (1) to provide for the continuous separation of overheadproduct consisting essentially of (B) and (C) and (3) recovering (B)from said overhead product of (2), where R, R, R" and a are aspreviously defined.

The present invention also is directed to silylorganocarbamates of theFormula 2, which can be made by (1) effecting reaction between asilylorganohalide, a metal cyanate and an aliphatic monohydric alcoholin the presence of an aprotic solvent, as shown by the followingequation,

(2) separating metal salts from the resulting mixture of (1) and (3)stripping the aprotic solvent from the resulting mixture of (2), WhereR, R, and R" are as defined above, X is a halogen radical, M is a metal,and y is the valence of the metal.

Radicals included by R of the above formulae are, for example, alkylradicals, such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl,and octyl. Radicals included by R are, for example, aryl radicals andhalogenated aryl radicals, such as phenyl, chlorophenyl, xylyl,naphthyl, etc.; aralkyl radicals such as benzyl, phenylethyl, etc.;alkyl radicals such as methyl, ethyl, propyl, hexyl, etc.; haloalkylradicals such as chloropropyl, difluoropropyl, bromobutyl, etc; alkenylradicals such as vinyl, allyl, 1 propenyl, etc.; cycloaliphatic andhaloaliphatic radicals such as cyclobutyl, cyclopentyl, cyclohexyl, etc.Radicals included by R" are, for example, alkylene radicals andhaloalkylene radicals such as methylene, ethylene, trimethylene,butylene, pentylene, halobutylene, etc.; arylenealkylene such as C H CHetc. In the above formulae, where R, R and R" can be more than oneradical, these radicals can be all the same, or any two or more of theaforementioned radicals.

Another aspect of the invention is directed to a method for makingisocyanurates of the formula,

where Q is (RO) ,,R'SiR"--, Which comprises (1) effecting reactionbetween (RO) R' SiR"X and M(NCO) in the presence of an aprotic solvent(2) removing metal salts from the resulting mixture of (1), and (3)stripping said aprotic solvent from the resulting product of (2).

Included by the silylorganoisocyanates of the Formula 1 are, forexample, tn'methoxysilylpropylisocyanate,phenyldiethoxysilylpropylisocyanate,methyldimethoxysilyl-butylisocyanate,ethoxydimethylsilylbutylisocyanate, etc. Some of thesilylorganocarbamates of Formula 2 are, for example, methylN-trimethoxysilylpropylcarbamate, ethylN-methyldimethoxysilylpropylcarbamate, ethylN-triethoxysilylbutylcarbamate, methylN-phenylmethylmethoxysilylpropylcarbamate, etc.

Alkylhalosilanes which can be utilized in the practice of the inventionare, for example, chloropropyltrimethoxysilane,bromopropyltrimethoxysilane, chlorobutyldimethylethoxysilane,chloropropyltriethoxysilane, chloropropylmethyldimethoxysilane,chlorobutylphenylmethyl npropoxysilane, iodopropyltrimethoxysilane, etc.Metal cyanates which can be employed in the practice of the invention,are for example, lithium cyanate, sodium cyanate, potassium cyanate,rubidium cyanate, barium cyanate, strontium cyanate, silver cyanate,lead cyanate, mercury cyanate, calcium cyanate, etc.

Some of the isocyanurates which are included by Formula 3 are, forexample, 1,3,5-tris(trimethoxysilylpropyl)isocyanurate,1,3,5-tris(methyldimethoxysilylpropyl) isocyanurate, 1,3,5tris(dimethylethoxysilylbutyl)- isocyanurate, 1,3,5-tris(phenylmethylmethoxysilylpropyl) silylpropylcarbamate, etc.

The silylorganoisocyanates of Formula 1 can be employed as caulkingcompounds when exposed to atmospheric moisture. They also can be used topolymerize hydroxylated organic polymers such as polyethers andpolyesters. The silylorganocarbamates of Formula 2 can be used as glasssizing materials, metal protectants, etc. Among the uses of theisocyanurates of Formula 3 are as adhesion promoters for roomtemperature vulcanizing compositions, as shown in my copendingapplication 669,284, filed concurrently herewith and assigned to thesame assignee as the present invention.

In preparing the silylorganocarbamates of Formula 2, thesilylorganohalide, aliphatic monohydric alcohol and metal cyanate aremixed together in a suitable aprotic solvent. Alcohols which can beemployed are, for example, methyl alcohol, ethyl alcohol, n-propylalcohol, n-butyl alcohol and other alcohols having from 1 to 8 carbonatoms. A suitable aprotic solvent is a solvent for the variousingredients required in the practice of the invention, which have noactive protons which may interfere with the formation of desiredproduct. Examples of aprotic solvents which can be employed in thepractice of the invention are preferably, for example,dimethylformamide, dimethylacetamide, N-methylpyrolidone,diethylacetamide, and diethylformamide. In addition, solvents such asethers, nitriles and ester, are operative, such as for example,ethyleneglycoldimethylether, dimethyleneglycoldimethylether,triethyleneglycoldimethylether, and tetraethyleneglycoldimethylether,benzonitlile, ethyl benzoate, tributylphosphate, etc. The order ofaddition of the various reactants is not critical. In order to avoidundesirable losses of reactants, as well as provide for optimum yieldsof desired product, substantially equal molar amounts of the variousreactants, for example, silylorganohalide alcohol, metal cyanate, etc.can be employed even though excesses, such as up to 10 molar excesses ofany of the reactants, will not adversely affect the formation of desiredproduct. In instances where a metal cyanate of a polyvalent metal isemployed, sufficient metal cyanate should be utilized to provide for atleast one mole of cyanate, per mole of silylorganohalide.

After the various ingredients have been mixed together, the resultingmixture can be brought to reflux to initiate the reaction. Experiencehas shown that a temperature in the range of between 90 C. to 140 C.will generally provide for effective results. Reaction times of from 3hours to 8 hours will be required depending upon the type and nature ofthe various reactants employed, and the temperature utilized during thereaction. One indication of ca-rbamate formation is the rise in thereflux temperature as the urethane starts to form. If desired, a vaporphase chromatograph of the reaction mixture can be taken to confirm thedisappearance of starting silylorganohalide and the appearance of thesilylorganocarbamate.

The conversion of the silylorganocarbamate to the correspondingisocyanate can be readily achieved. The silylorganocarbamate can becracked by heating it to reflux under reduced pressure to provide forthe initial separation of the aliphatic monohydric alcohol. For example,pressure such as 0.25 mm. to 500 mm. can be employed, while atemperature in the range of C. to 200 C. has been found efiective. Thealcohol can be caught in a trap, such as a Dry Ice trap. With properadjustment of the reflux ratio, there can be achieved continuouscracking of the silylorganocarbamate, and continuous separation of thesilylorganoisocyanate as an overhead product. The cracking temperatureof the silylorganocarbamate and the proper reflux ratio can be bestdetermined by initially bringing the silylorganocarbamate to reflux in asuitable fractionating column under reduced pressure, while providingfor the continuous separation of the aliphatic monohydric alcohol.

Experience has shown that if the silylorganocarbamate is heated toorapidly, i.e., without proper reflux control to provide for theseparation of overhead product and return of silylorganocarbamate,isocyanurate of Formula 3 can be formed along with isocyanate ofFormula 1. To avoid isocyanurate formation, careful control of thereflux of the silylorganocarbamate must be observed.

The preferred method of making the isocyanurate of Formula 3 is byheating a mixture of the silylorganohalide and metal cyanate and anaprotic solvent to a temperature between C.250 C. and preferably 130C.160 C., in the absence of the aliphatic monohydric alcohol. Prior tostripping the isocyanurate of aprotic solvent, removal of metal saltsfrom the mixture has been found expedient.

In order that those skilled in the art may be better able to practicethe invention, the following examples are given by way of illustrationand not by way of limitation. All parts are by weight.

EXAMPLE 1 A dimethylformamide solution of a mole ofchloropropyltrimethoxysilane, 1.2 moles of potassium cyanate and 2 molesof methanol was heated to reflux. The solution consisted of two parts ofsolvent, per part of the total weight of reactants. The mixture wasrefluxed for a period of 6 to 8 hours. The temperature of the mixturegradually climbed from 90 C. to C. A vapor phase chromatograph of themixture showed almost the complete absence of thechloropropyltrimethoxysilane. The mixture was refluxed for an additionaltwo hours. The mixture was then allowed to cool and it was filtered. Thesolvent was then flashed distilled. The resulting material was thenfractionated. There was obtained an 85% yield of a product having aboiling point of 90 C. at 1.4 mm. Hg. Based on method of preparation andits infrared spectrum, the product was methylN-trimethoxysilylpropylcarbamate.

Methyl N-trimethoxysilylpropylcarbamate is applied to glass fibers byspraying them with a 2% methanol solution. The treated fibers are thenheated in contact with a sheet of silicone rubber under pressure. Aglass reinforced rubber composite is produced.

EXAMPLE 2 There was heated to 160 C., 119 parts of methyltrimethoxysilylpropylcarbamate. A vacuum of 1 mm. was maintained during theheating. The mixture began to reflux, and a first reaction product wascontinuously recovered overhead at a temperature of 84 C. In addition, amore volatile second product was continuously caught in a Dry-Ice trap.Reflux and product recovery was continued for an additional five hours.There was obtained 75 parts of the first reaction product. Based on itsmethod of preparation, its infrared spectrum showing isocyanateabsorption at 4.58 microns, and the total absence of urethane absorptionat 5.78 microns, the first reaction product wastrimethoxysilylpropylisocyanate.

EXAMPLE 3 A mixture of 40 parts of chloropropyltrimethoxysilane,

50 parts of anhydrous dimethylformamide and 16.2 parts of potassiumcyanate was heated to C. at atmospheric pressure. After heating for 4hours a vapor phase chromat ograph showed the complete absence of theoriginal starting material. The reaction mixture was then allowed tocool and it was filtered. It was then stripped of solvent. The resultingproduct was distilled at 236 C. at 0.2 mm. Hg. There was obtained 35parts of product which represented a yield of about 86% based on thestarting reactants. Based on its method of preparation and its infraredspectrum, the product was 1,3,5-tris(trimethoxysilylpropyl) isocyanurate.

EXAMPLE 4 A mixture of 36.4 parts of chloropropyldimethoxymethylsilane,16.2 parts of potassium cyanate and 50 parts of dimethylformamide, washeated in accordance with the procedure of Example 3. After a period ofabout 5 hours at 140 C., a vapor phase chromatograph of the mixtureshowed the complete absence of the original starting materials. Therewas obtained a yield of about 82% of product which was distilled at 221C. at 0.25 mm. Hg. Based on its method of preparation and its infraredspectrum, the product was 1,3,5-tris(dimethoxymethylpropyl)isocyanurate.

EXAMPLE 5 A reaction mixture consisting of 36.4 parts ofchloropropylmethyldimethoxysilane, 17 parts of potassium cyanate 6.4parts of anhydrous propanol and 75 parts of dry dimethylformamide isallowed to reflux at atmospheric pressure under a dry atmosphere. Thereflux temperature rises from 90 C. to 125 C. for a period of about 6hours. A vapor phase chromatograph shows complete absence of startingmaterial and appearance of a new peak. A product is recovered followingthe procedure of Example 1. It is propylN-dimethoxysilylpropylcarbamate, based on its method of preparation andits infrared spectrum.

Propyl N-dimethoxysilylpropylcarbamate is then heated under reducedpressure and fractionated. Propanol is collected in a Dry Ice trap. Asecond product distills overhead. Based on its method of preparation andits infrared spectrum showing a strong absorption band at 4.58 microns,the product is methyldimethoxysilylpropylisocyanate.

EXAMPLE 6 A carbamate reaction mixture of 29.2 parts ofp-phenyldimethoxysilylchloromethylbenzene, 11.1 parts of barium cyanate,5 parts of methanol and 75 parts of N-methylpyrolidone is heated toreflux. The p-phenyldimethoxysilylchloromethylbenzene is prepared byinitially reacting one mole of p-tolylmagnesium chloride with two molesof phenyltrichlorosilane in tetrahydrofuran at a temperature between 40C.60 C. The resulting phenyl, p-tolyl substituted dichlorosilane isthereafter chlorinated in the presence of ultraviolet light andalkoxylated with methanol in the presence of pyridine.

The course of the above described carbamate reaction is followed with avapor phase chromatograph. At the completion of the reaction, themixture is allowed to cool and 6 filtered of salts. The solvent isremoved by flash distillation. Based on method of preparation, there isobtained methyl- N-4-dimethoxyphenylsilylbenzyl carbamate.

While the foregoing examples have of necessity been limited to only afew of the very many variables within the scope of the presentinvention, it should be understood that the present invention covers amuch broader class of silylorganocarbamates as shown by Formula 2, andmethods for making the corresponding isocyanates of Formula 1, andisocyanurates of Formula 3.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A method for making silylorganocarbamates of the formula(R0)3&R'=S1R"NHH1OR where R is selected from alkyl radicals having from1 to 8 carbon atoms, R' is a member selected from the class consistingof monovalent hydrocarbon radicals, and halogenated monovalenthydrocarbon radicals, R" is selected from the class consisting ofdivalent hydrocarbon radicals and halogenated divalent hydrocarbonradicals, and a is a whole number equal to from 0 to 3, inclusive, whichcomprises (1) effecting reaction between a silylorganohalide, a metalcyanate and an aliphatic monohydric alcohol in the presence of anaprotic solvent and, (2) separating metal salts from the resultingmixture of (1) and, (3) stripping said aprotic solvent from theresulting mixtures of (2).

2. A method of claim 1 for makingmethyl-N-trimethoxysilylpropylcarbamate, which comprises, (1) heating toreflux, a mixture of chloropropyltrimethoxysilane potassium cyanate andmethanol in the presence of dimethylformamide, (2) separating potassiumsalts from (1) and, (3) stripping dimethylformamide from the resultingmixtures of (2).

3. A method of claim 1 for making methyl-N-methyldimethoxysilylpropylcarbamate which comprises, (1) heating toreflux a mixture of chloropropylmethyldimethoxysilane potassium cyanateand methanol in the presence of dimethylformamide, (2) separatingpotassium salts from 1) and, (3) stripping dimethylformamide from theresulting mixture of (2).

References Cited UNITED STATES PATENTS 3,170,891 2/1965 Speier 260-4488XR 3,288,754 11/1966 Green 260448.8 XR

DELBERT E. GANTZ, Primary Examiner P. F. SHAVER, Assistant Examiner US.Cl. X.R.

